Why there is a need for bonds for atoms?
The necessity for atoms to form bonds arises from a fundamental principle governing stability in the natural world. Achieving stability involves attaining the electronic configuration found in noble gases (He, Ne, or Ar), characterized by having 2 or 8 electrons in the valence shell—an indicator of stability. The attainment of 2 electrons follows the duplet rule, while reaching eight electrons adheres to the octet rule.
Noble gases, being stable, possess valence shells fully filled with either 2 or 8 electrons, leaving no room for additional electrons. Consequently, noble gases neither gain, lose, nor share electrons, rendering them non-reactive. This inertness stems from their valuable electronic configuration, coveted by other atoms.
In pursuit of this stable noble gas electronic configuration, atoms engage in chemical bonding, a phenomenon where atoms combine with each other. In simple terms, atoms form chemical bonds to achieve stability by acquiring the inert gas electronic configuration. An atom can accomplish this by offering valence shell electrons to other atoms, acquiring electrons from others (if the valence shell has five or more electrons), or sharing valence electrons with neighboring atoms. These bonding mechanisms allow atoms to attain the coveted stability reflected in the noble gas electronic configuration, where the valence shell accommodates 8 electrons, realized through various methods.
Chemical Bond Definition
A chemical bond is defined as a force of attraction between atoms that holds them together in a compound. In other words, during bond formation, there is some force that holds the atoms together.
Types of Chemical Bond
The valence electrons, which are associated with chemical bonding, are described as bonding electrons. They normally reside in the incomplete or partially filled outermost shell of an atom. Depending upon the method of how these valence electrons are involved in bonding, they result in the following four kinds of chemical bonds:
- Ionic Bond
- Covalent Bond
- Dative Covalent or Coordinate Covalent Bond
- Metallic Bond
Learn about Covalent bond and Dative Covalent or Coordinate Covalent Bond
Ionic Bond
The elements of Group-1 and Group-2 being metals have the tendency to lose their valence electrons forming positively charged ions. Whereas non-metals of Group- 15 to Group-17 have the tendency to get or accept electrons. They are electronegative elements with high electron affinities.
If atoms coming from these 2 different groups, metals and non-metals, are enabled to react, a chemical bond is formed. This type of chemical bond, which is formed due to the complete transfer of an electron from one atom to another atom, is called ionic bond.
The development of NaCl is a fine example of this kind of bond.
Salt is a simple compound formed by Sodium (Z =11) and chlorine (Z= 17) atoms. The ground state electronic configuration of these components is shown listed below:
The frames show electrons in the valence shells of these elements; sodium has only one electron and chlorine have 7 electrons. Sodium being an electropositive element has the propensity to lose electron and chlorine being an electronegative element has the tendency to acquire electron. Therefore, they form positive and negative ions by losing and acquiring electrons, respectively. They attain the electronic configuration of the nearby noble gases.
By losing one electron from the outer shell, sodium becomes Na+ ion and it is entrusted to 8 electrons in the 2nd shell which will now become the valence shell. By acquiring one electron, the chlorine atom now also has eight electrons in its outermost shell and ends up being CI– ion. Both of these atoms are now changed into oppositely charged ions. They support themselves by integrating with each other due to the electrostatic force of attraction between them such as:
It is to be kept in mind that only valence shell electrons take part in this kind of bonding, while other electrons are not included. In such kind of reaction, heat is usually given out. The compounds formed due to this kind of bonding are called ionic compounds.
Metallic Bond
The metallic bond is defined as a bond formed in between metal atoms (positively charged ions) due to mobile or free electrons.
The different properties shown by metals such as high melting and boiling points, excellent conductions of heat and electrical energy, tough and heavy nature, suggest the existence of various kinds of chemical bonds between atoms of metals.
In the case of metals, the hold of the nucleus over the outermost electrons is weak because of large-sized atoms and a greater number of shells in between the nucleus and valence electrons. Moreover, because of low ionization capacities, metals have the propensity to lose their outermost electrons quickly. Resultantly, these loose or free electrons of all metal atoms move easily in the spaces between atoms of metal.
None of these electrons is connected to any particular atom. Either they come from a typical pool or belong to all the atoms of that metal. Nuclei of metal atoms appear submerged in sea of these totally free mobile electrons. These mobile electrons are accountable for holding the atoms of metals together forming a metal bond.
FAQs: Chemical Bonding: Ionic Bond & Metallic Bond
- Why do atoms need to form bonds?
- Atoms seek stability by achieving the electronic configuration of noble gases (2 or 8 electrons in the valence shell). Noble gases are non-reactive because their valence shells are full. Atoms form bonds to gain this stability, either by giving, taking, or sharing electrons.
- What is a chemical bond?
- A chemical bond is a force of attraction between atoms that holds them together in a compound. It is the force responsible for keeping atoms connected during bond formation.
- What are the types of chemical bonds?
- Chemical bonds are classified into four types based on the involvement of valence electrons: Ionic Bond, Covalent Bond, Dative Covalent or Coordinate Covalent Bond, and Metallic Bond.
- What is an Ionic Bond?
- Ionic bonds form between metals (Group-1 and Group-2) and non-metals (Group-15 to Group-17). This bond involves the complete transfer of electrons from a metal atom to a non-metal atom, resulting in the formation of oppositely charged ions.
- Can you provide an example of an Ionic Bond?
- Sodium (Na) and chlorine (Cl) react to form the ionic compound NaCl (table salt). Sodium loses one electron to become Na+ ion, and chlorine gains that electron to become Cl– ion.
- What is a Metallic Bond?
- Metallic bonds occur between metal atoms, where positively charged metal ions are held together by a sea of mobile electrons. These electrons are not tied to any specific atom and contribute to the unique properties of metals.
- What properties are associated with Metallic Bonds?
- Metallic bonds contribute to properties like high melting and boiling points, excellent heat and electrical conductivity, as well as the malleability and toughness observed in metals.
- Why do metals have a tendency to lose electrons?
- Metals tend to have weak nucleus-electron attraction due to large-sized atoms and a greater number of shells. Additionally, metals have low ionization capacities, making it easier for them to lose outermost electrons and form positive ions.
- Do all valence electrons participate in chemical bonding?
- In ionic bonding, only valence shell electrons are involved, while other electrons are not. This selective participation in bonding leads to the formation of ionic compounds.
- What happens during the formation of an ionic compound?
- Ionic compounds are formed by the electrostatic force of attraction between oppositely charged ions (e.g., Na+ and Cl–) resulting from the transfer of valence shell electrons. This process often releases heat.
Multiple Choice Questions (MCQs) with Answers: Chemical Bonding
- Why do atoms form chemical bonds?
- a) To become radioactive
- b) To achieve stability by acquiring electronic configuration of noble gases
- c) To increase reactivity
- d) To form inert gases
Answer: b) To achieve stability by acquiring electronic configuration of noble gases
- What is the significance of having 2 or 8 electrons in the valence shell?
- a) It makes atoms radioactive
- b) It indicates stability
- c) It increases electronegativity
- d) It prevents chemical reactions
Answer: b) It indicates stability
- Which rule describes the attainment of 2 electrons in the valence shell?
- a) Octet rule
- b) Duplet rule
- c) Triplet rule
- d) Quintet rule
Answer: b) Duplet rule
- In chemical bonding, what does the term “duplet” refer to?
- a) Two atoms forming a bond
- b) Two electrons in the valence shell
- c) Two types of atoms involved
- d) Two different chemical bonds
Answer: b) Two electrons in the valence shell
- What is the primary reason for atoms to combine, leading to chemical bonding?
- a) To increase reactivity
- b) To achieve stability by acquiring inert gas electronic configuration
- c) To form unstable compounds
- d) To become noble gases
Answer: b) To achieve stability by acquiring inert gas electronic configuration
- How can an atom accommodate 8 electrons in its valence shell?
- a) By losing valence shell electrons
- b) By acquiring electrons from other atoms
- c) By sharing valence electrons with other atoms
- d) All of the above
Answer: d) All of the above
- Which of the following is NOT a type of chemical bond?
- a) Ionic Bond
- b) Covalent Bond
- c) Ionic Covalent Bond
- d) Metallic Bond
Answer: c) Ionic Covalent Bond
- What defines a chemical bond?
- a) A force of attraction between atoms that repels them
- b) A force of attraction between atoms that holds them together
- c) A force of repulsion between electrons
- d) A force of repulsion between atoms
Answer: b) A force of attraction between atoms that holds them together
- Which type of bond involves the complete transfer of an electron from one atom to another?
- a) Covalent Bond
- b) Dative Covalent Bond
- c) Ionic Bond
- d) Metallic Bond
Answer: c) Ionic Bond
- In the formation of NaCl, which element loses an electron?
- a) Sodium (Na)
- b) Chlorine (Cl)
- c) Both Na and Cl
- d) Neither Na nor Cl
Answer: a) Sodium (Na)
- What is the charge on the chlorine ion in NaCl?
- a) Positive
- b) Negative
- c) Neutral
- d) Variable
Answer: b) Negative
- Which electrons participate in ionic bonding?
- a) All electrons
- b) Inner shell electrons
- c) Valence shell electrons
- d) Duplet electrons
Answer: c) Valence shell electrons
- What is the result of losing one electron from the outer shell of sodium in the formation of NaCl?
- a) Sodium becomes a negative ion
- b) Sodium becomes a positive ion
- c) No change in sodium’s charge
- d) Sodium becomes neutral
Answer: b) Sodium becomes a positive ion
- What is the nature of compounds formed by ionic bonding?
- a) Covalent compounds
- b) Metallic compounds
- c) Ionic compounds
- d) Non-reactive compounds
Answer: c) Ionic compounds
- What is the primary force responsible for holding atoms together in a metallic bond?
- a) Electrostatic force
- b) Covalent force
- c) Magnetic force
- d) Van der Waals force
Answer: a) Electrostatic force
- Why do metals have a tendency to lose electrons easily?
- a) Due to high electronegativity
- b) Due to weak nucleus-electron attraction
- c) Due to small-sized atoms
- d) Due to high ionization capacities
Answer: b) Due to weak nucleus-electron attraction
- What contributes to the unique properties of metals in a metallic bond?
- a) Fixed electrons in orbits
- b) Mobile or free electrons
- c) Covalently bonded electrons
- d) Ionically bonded electrons
Answer: b) Mobile or free electrons
- Which type of bonding is responsible for high melting and boiling points in metals?
- a) Covalent Bond
- b) Ionic Bond
- c) Metallic Bond
- d) Dative Covalent Bond
Answer: c) Metallic Bond
- In metallic bonding, where do free electrons move?
- a) Within fixed orbits
- b) In specific shells
- c) In spaces between atoms
- d) Attached to specific atoms
Answer: c) In spaces between atoms
- What is the role of mobile electrons in metallic bonding?
- a) To attract positively charged ions
- b) To repel atoms
- c) To hold metal atoms together
- d) To absorb heat energy
Answer: c) To hold metal atoms together
Summary: Chemical Bonding – Ionic Bond & Metallic Bond
The tutorial begins by addressing the universal principle that stability is sought after in the natural world. Atoms achieve stability by obtaining the electronic configuration of noble gases, typically with 2 or 8 electrons in the valence shell, known as the duplet and octet rules. Noble gases, with their fully filled valence shells, do not engage in electron gain, loss, or sharing, rendering them non-reactive.
Atoms, aiming for stability, form chemical bonds through processes such as offering valence shell electrons, acquiring electrons from others, or sharing valence electrons. This drive for stability leads to the formation of chemical bonds, a crucial aspect explained in the tutorial.
The concept of a chemical bond is defined as a force of attraction between atoms that binds them into compounds. The tutorial further introduces the four types of chemical bonds based on the involvement of valence electrons: Ionic Bond, Covalent Bond, Dative Covalent or Coordinate Covalent Bond, and Metallic Bond.
The Ionic Bond section explores the interaction between metals (Group-1 and Group-2 elements) and non-metals (Group-15 to Group-17 elements). The example of sodium chloride (NaCl) formation illustrates the complete transfer of an electron from sodium to chlorine, resulting in the formation of oppositely charged ions, which attract each other due to electrostatic forces.
The Metallic Bond section explains how metal atoms, characterized by weak nucleus-electron attraction and a tendency to lose electrons easily, form bonds through mobile or free electrons. These mobile electrons move freely between metal atoms, contributing to various properties like high melting and boiling points, electrical conductivity, and toughness.
In summary, the tutorial provides a comprehensive overview of chemical bonding, emphasizing the pursuit of stability in atoms and the diverse mechanisms through which bonds are formed, including iconic and metallic bonding.